Dry powder inhalers such as those described in U.S. Pat. Nos. 7,305,986, 7,464,706 and U.S. patent application Ser. No. 12/484,129 (2009/0308391), which disclosure is incorporated herein by reference in their entirety, can generate primary drug particles or suitable inhalation plumes during an inspiratory maneuver by deagglomerating the powder formulation within a container, capsule, or a cartridge. Dosing reproducibility requires that the drug formulation is uniform and that the dose can be delivered to the patient with consistent and reproducible results. Therefore, the dosing system must operate to completely discharge all of the formulation effectively during an inspiratory maneuver when the patient is taking his/her dose. The benefits of delivering drugs via the pulmonary circulation are numerous and include, rapid absorption into the arterial circulation, avoidance of drug degradation by liver metabolism, ease of use, i.e., lack of discomfort of administration, such as discomfort encountered by other routes of administration such as by injection.
The consistency in drug delivery from an inhaler is due in part to the consistency in resistance to air flow within the air passages of the inhalation device. High resistance dry powder inhalers such as those disclosed in U.S. Pat. Nos. 7,305,986 and 7,464,706, and U.S. patent application Ser. No. 12/484,129 (2009/0308391), deliver drug formulations in a consistent manner. One of the parameters used to ascertain or predict if an inhaler would deliver a dose with consistency during use is by knowing the resistance to air flow of the device, which can be measured or determined after the device is manufactured.
Present systems and methods for measuring the resistance to air flow through an inhaler are cumbersome, involve numerous steps and calculations and are subject to variations in ambient conditions. Therefore, the inventors have seen the need to design and manufacture a simple apparatus, system, and method for measuring the resistance to airflow of an inhaler in order to determine if the inhaler resistance properties would render the inhaler suitable for use. The present system allows for a rapid method for measuring the resistance of inhalation systems or the individual inhalers, in an integrated system using a few simple steps.